The invention relates to a monitoring device for monitoring safety components, comprising monitoring electronics which include a plurality of clock generators and evaluation means and on which at least two interfaces to be monitored for electric coupling to safety components are formed, wherein each of the interfaces comprises at least two output ports and at least two input ports, wherein each of a first output port and a second output port is connected to a clock generator designed for providing clocked electric monitoring signals, wherein a first input port and a second input port are connected to the evaluation means designed for an evaluation of incoming monitoring signals and for an output of a fault message when provided monitoring signals fail to appear. The invention further relates to a safety system and a method for operating a safety system.
From EP 0864875 A2, a method for checking a safety circuit for electric loads such as electric machines, in particular presses or the like, for short-circuits and/or faults is known. In this method, the safety circuit comprises at least one control output and at least one input, the number of inputs preferably differing from the number of control outputs. In the execution of the method, it is provided that each control output emits an output signal, that the output signals are fed as input signals to the input ports and that each output signal is used for checking for a potential short-circuit. It is further provided that several, at least two, output signals are used in parallel, i.e. substantially simultaneously during a phase, for checking for a potential short-circuit between two inputs, and that the total number of output signals in several consecutive phases is checked, each phase being used for checking several, at least two, output signals and/or input signals.
In prior art, it is provided that an individual clock generator is assigned to each of the outputs connected to a clock generator. In a further example of prior art known to the applicant but not available as a document, it is provided that first outputs of all interfaces are connected to a first clock generator and second outputs of all interfaces are connected to a second clock generator.